In recent years, electronic devices are becoming more and more multi-functionalized, downsized, and digitalized. In such circumstances, an electronic device exhibits its functions by a combination of a large number of semiconductor devices. The demand for advanced multi-functionality of semiconductor devices makes their processes complicated, which promotes an increase in operating speed. In order to respond to the demands for high-speed operation and downsizing of semiconductor devices, the semiconductor manufacturing process becomes finer and the operating voltage becomes lower, but the current tends to increase. Along with the decrease in operating voltage, a technology of suppressing fluctuations in power supply potential has become essential.
Measures taken to suppress the fluctuations in power supply potential are to arrange a bypass capacitor very close to a semiconductor device and to connect by thick and short wiring or a large number of vias. The purpose is to reduce an inductance component of power supply wiring. The inductance of the power supply wiring adversely affects the fluctuations in power supply potential. This is because counter-electromotive force is generated by a current flowing in the power supply wiring based on the inductance component of the power supply wiring, to thereby cause the fluctuations in the power supply potential. In an electronic device, a large number of such semiconductor devices capable of performing high-speed operation are mounted on a printed wiring board.
In order to realize downsizing, the semiconductor devices and the bypass capacitor are arranged very close to one another. The power supply wiring to be wired is thick and short in order to achieve the low inductance, but the power supply potential may fluctuate in the semiconductor device to no small extent. It is common practice that the fluctuations in the power supply potential in the operating semiconductor device itself are controlled by the low inductance. In the electronic device, another semiconductor device arranged in the vicinity of the semiconductor device also operates at high speed with a similar low voltage. As the operating voltage becomes lower, concern is growing that the fluctuations in the power supply potential generated from one semiconductor device itself may adversely affect another semiconductor device to cause a malfunction or the like.
As the countermeasure, in PTL 1, in order to improve an effect of suppressing high-frequency power supply noise superimposed on a power supply system, there is proposed a technology relating to a power supply noise filter structure of a printed wiring board having a capacitor mounted thereon. In PTL 1, power supply wiring is divided into two parts, and one of the two terminals of the capacitor is connected across the two parts of the power supply wiring while the other terminal is connected to ground wiring. In this manner, bypass performance of the capacitor is improved.